Can you change the render seed for each frame of an animation in cycles?
New Versions of Blender

As of 2.75, this is as simple as checking the little clock icon in the seed input field.



Previous Versions of Blender

You can animate and add drivers to the seed field in the Sampling panel in the render buttons the same way you can with most of the fields in Blender. Simply clicking on the field and writing #frame will create a driver that uses the current frame number as the value for the field. This generates a different noise pattern for each frame.